1. Technical Field
The present invention relates to an overcharge protection apparatus with minimized power consumption.
2. Description of the Related Art
Generally, a lithium-ion battery that is a rechargeable battery may explode or ignite when overcharged to a predetermined voltage or more. Further, a battery module typically includes multiple battery cells to acquire a required output. If at least one of the battery cells included in the battery module is overcharged to explode or ignite, not only the corresponding battery cell which has been overcharged, but also remaining battery cells are also influenced, and thus it is essential to prevent the overcharge of a battery in order to guarantee the safety of the battery.
An electrical overcharge protection apparatus is connected to one of the cells included in a battery module and continuously monitors the voltage of the battery cell. Such an electrical overcharge protection apparatus is configured to, when the battery cell is overcharged and the voltage of the battery cell increases above a predetermined voltage, release connection between the battery module and a charging power source.
However, a conventional electrical overcharge protection apparatus is disadvantageous in that it is always electrically connected to the battery cell so as to monitor the voltage of the battery cell, thus steadily consuming constant power.
Therefore, when the battery is left as it is for a long period of time, there occurs a difference between the voltage of the battery cell, for which overcharge is detected, and the voltages of the remaining cells due to the power consumption of the electrical overcharge protection apparatus.
Since a large-capacity battery cell has a large storage capacity, a difference between the cell voltages is not very large. However, since a small-capacity battery cell has a small storage capacity, a voltage difference relatively increases, thus shortening the lifespan of the battery due to the degradation of the battery cell.
The following patent document described in the prior art documents relates to a power system that is capable of reducing a dark anent flowing through a state monitoring circuit while assigning a state monitoring function using the state monitoring circuit, in a power system having multiple storage batteries and a semiconductor switching element as an opening/closing means. In the following patent document, when the power of a vehicle is turned off metal-oxide-semiconductor (MOS) switches 21 and 22 are turned off, so that current is prevented from flowing into a voltage detection circuit 40 from respective storage batteries 12 and 13 through the semiconductor switch units of respective MOS switches 21 and 22, thus reducing a dark current in the power-off state of the vehicle.